Method for inserting tubular linings or draw-strings into conduits



United States Patent Ofiiee 3,119,599 Patented Jan. 28, 1964 3,119,599 METHOD FOR INSERTING TUBULAR LININGS R DRAW-STRINGS INTO CONDUITS Wiiliam I. Tattle, Toronto, ntario, Canada, assignor to Canadian General Electric Company, Limited, Toronto,

Ontario, Canada, a company of Canada Filed Nov. 7, 1960, Ser. No. 67,814 4 Ciaims. (Cl. 25d-134.4)

My invention relates to means for projecting a length of flexible tubing through a conduit in continuous form from one end to the other, either for the purpose of lining such conduit to render it fluid impervious and hence capable of having fiuid materials conveyed therethrough without loss, or for functioning as a draw-string whereby a follower-line subsequently attached to one end of the tubing may be pulled through the conduit either while the tubing remains in unwound or tubular form or after the same has been twisted into twine-like condition.

A further object is to provide a device for placing an airtight liner or tube in a conduit, either to prevent leakage, or alternatively, to permit changes of quality or kind of fluid passing through such conduit without contamination by the residue from a previous quality or kind, and this by simply replacing the liner with a successive liner.

Specifically, as at present envisioned, my invention is designed to replace the conventional system of rodding all types of underground conduit such as telephone conduit between adjacent manholes to reduce the cost of the total operation of pulling cables therethrough, as well as to permit the construction of fewer manholes and instead permit longer uninterrupted runs of conduit between adjacent manholes than is now possible.

A further object of my invention is to provide means whereby a conduit laying contract can be vertified as to its freedom from blockages, quickly and inexpensively as soon as it is completed. Additionally, in this connection, at the same time as such a test is made, a steel follower string can be pulled through the conduit after attachment to one end of the tubing as aforesaid in readiness for pulling through the cables at any time later.

With the foregoing objects in view, and such other objects as may become apparent as this specification proceeds, my invention consists in the following arrangement and construction of parts and the following steps in the concerned process all as hereinafter more particularly described reference being had to the accompanying figures in which:

FIGURE 1 is a schematic plan representation of a subterranean conduit including two 90 degree curves, and intake and exit manholes at the ends of said conduit.

FIGURE 2 is a fragmentary cross-sectional elevation of a section of conduit including the intake manhole end thereof, with my projectile and tubing in situ, the latter being depicted for clarity in conventionalized or schematic form and somewhat expanded as to the leading end or accordion pleated portion, the better to exemplify the depth of the pleating which is sufficient to seal the tubing against the existence of any central passageway through which air could pass to cause a premature blow-ou in advance of the inflated trailing tubing.

FIGURE 3 is a fragmentary cross-sectional representation of a conduit including both the intake and exit manhole ends thereof, indicating the manner in which my tubing is anchored at the exit or discharge end of the conduit, and is converted into twine-like form from the opposite or intake manhole end of the conduit.

In the drawings like characters of reference designate similar parts in the several figures.

The average distance between telephone conduit manholes in heavily congested city area is 600 feet. In suburban areas the distance between manholes may be greater.

My invention contemplates the practicability of manholes spaced up to 1600 feet apart and the possibility that the conduit extending between them may be serpentine to the extent of two 90 degree curves of 30 foot radius.

The conventional method of preparing for the pulling through of cables from one manhole to the next is by rodding By this is meant the projection end-wise of Successive snapped-on sections of rod through the conduit from an intake manhole to the next or exit manhole. 600 to 700 feet represents the practicable limit of the amount of rodding which it is possible to push, and, altogether, the method is expensive and slow.

The projection of a bullet or plug of substantially the diameter of a conduit, and having attached thereto a draw-string, through a conduit by the introduction of compressed air behind the bullet has on occasion been resorted to. This method however is unsatisfactory for use in multiple duct because it is formed of sections as best depicted in the accompanying FIGURE 2 with air `spaces between the sections, and in multiple, by which I mean that conduits are customarily laid in sets of several parallel and adjacent single conduits. Because of this, it is obvious that compressed air can escape from between the sections forming one conduit and into the adjacent conduits between the sections which form these also. For simplicity I have shown in the accompanying drawings a single conduit. Multiple conduit however, as is well known by those skilled in the art to which this invention relates, consists of single, sectional castings each having, most commonly, 2 or more 3 inch or 31/2 inch area apertures therein each of which constitutes a single section of conduit.

- Preliminary Description Essentially my invention comprises a projectile within which s packed plastic film in tubular form in such manner that when the trailing end of the tubing is secured to the intake end of a conduit and air introduced as from the blower depicted in the accompanying FIGURE 1, the tubing becomes inflated, causing the projectile to travel along the conduit and unpacking from the rear end thereof as the projectile proceeds to the next manhole. When thel projectile emerges from the exit manhole end of the conduit, the leading end (hitherto sealed) is cut open and anchored in'open position (see accompanying FIGURE' 3) to permit the escape of air while the tubing is converted into twine-like form by means of a rotary drillor the like at which the opposite end of the tubing is suitably tied. When the tubing has been converted into twine ofcourse, a follower-string can be attached to either end and pulled through by means of the said draw-string, and,

eventually, the permanent cable.

Thus it will be recognized that another novel feature of my method is to ensure thatthe friction between the conduit and the projectile during travel of the latter, is

lessened as the distance from the starting point increases.,

This is achieved by virtue of the fact that there is nothing being pulled through the conduit. The projectile exudes a trail of tubular film so to speak as it proceeds, and it is therefore losing the weight of its contents and consequent resistance against the conduit wall with each foot of travel.

Complete Description In detail, my invention comprises the means and method embodied in the component parts and steps involving the use thereof as follows:

The main components involved in my means and method comprise a conventional conduit, intake manhole and exit manhole, 1, 2, and 3 respectively, the projectile collectively designated 4, the tubing 5 which may variously hereinafter be referred to as a tube-string, draw-string or the like, means 6 for anchoring tubing 5 at the intake manhole end, means 7 for the same purpose at the exit manhole end, and a blower 8.

Projectile 4 in detail comprises (in a presently preferred form) one or more similar sections 9, 9A, 9B. etc., according to however many are required in the formation of a train of same to construct an articulated projectile. At opposite ends of each section are male and female interconnecting portions 10 and 11 to permit limited universal movement as between the sections. As will be best observed from the accompanying FIGURE 2, the ball and socket connections (which I collectively designate 12) are of greater diameter than the main (and cylindrical) body portion 13 of the sections. In virtue of this, I provide a minimum amount of friction as between my projectile and the inner surface of conduit 1.

While I do not wish to be confined to any particular material for the manufacture of my projectile, I presently employ polyethylene resin largely because of the flexibility provided thereby at the ball and socket connections 12 whereby same may be snapped together and pulled apart with ease and yet remain satisfactorily connected during a journey along a conduit between adjacent manholes.

While I might provide a leading section 9 having a more or less bullet shaped nose, I generally prefer to attach a separate leading section or nose-piece 14 provided like the aforesaid trailing sections with a semi-spherical male (or if preferred female) portion 15 and having therein a grommetted lug 15A spanning the interior of element 14 diametrically to provide in effect an eyeletted tab through the eyelet 16 of which, the leading, twisted and hence sealed end 17 of tubing 5 may be secured.

While it is necessary to seal the leading end of tubing in order that the same may be projected on its way, it is not essential that the tubing be connected to my proectile excepting for the possible occasional need to retract the same for any reason.

'Tubing 5 may be of a variety of suitable flexible materials, that which I presently consider .to be most suitable being polyethylene lrn as manufactured in tubular form. It presently appears as if the diameter of such tubing should be less than the interior diameter of my projectile `4 and, when inflated, should be of sufficient tensile strength radially to contain, without distention against the interior wall of the conduit, the volume of air to be introduced thereinto.

For short distances between manholes, tubing 5 may be packed more or less haphazardly within a projectile but for long runs, same should be pre-packed into accordion form. In this connection also, although it may prove satisfactory with tubing of some materials and up to certain lengths to accordion-pleat the same by zig-zagging it while flattened, I deem it preferable to compress tubing 5 into pre-packed form by a process of annular accordionpleating 18.

Such accordion-pleating being deep, eliminates any central airway. Therefore the air pressure is always applied to the rear end of the remaining packed portion of the tubing 5. Without eliminating such a central air-way, air would tend to push the projectile forward in the sense that the projectile would be to a certain extent pulling the accordion-pleated tubing from the front end thereof, and such air, expanding outwardly with the still packaged or pleated portion would tend to blow it out of its carefully pre-packed form instead of opening it in a steady trailing form from the rear end of the remaining packaged portion. Preferably therefore tubing 5 will be made available in lengths possibly of several feet in the compressed annularly pleated form just described and enclosed within a disposable plastic envelope 19. Thus, portions may be cut according to need from such a length and inserted into projectile 4, or, stated another way, projectile 4 in as many sections as may be deemed necessary can be slipped over a length of pre-packed tubing, minus of course the nose-piece or leading section 14 which will be attached as 4 the next step after tying the end of the tubing thereto as already explained.

In carrying out the process for which the foregoing components have been designed, a projectile loaded with -pre-packed tubing is inserted into the intake end Z0 of a conduit 1. The trailing end 22 may then be secured around the end of the conduit as by means of the element 6 already referred to and which functions as an anchoring plug provided with a central aperture 23. Air at low pressure is now injected into tubing 5 at high velocity and in high volume. Such is accomplished by a blower 8 already referred to in the form for instance of an industrial-type (multi-stage) vacuum cleaner wherein of course the exhaust would be attached to aperture 23.

By the expressions fluid material, and gaseous uid and the like as in the accompanying claims I include (in the rst expression) suspensions of solids in liquid such as wood pulp, and (in both expressions) air or any gas which may be found to be particularly suited to the exercise of the present invention. Preferably, according to present indications, each of my projectile sections 9 should contain pre-packed tubing equivalent to about feet extended. It is also advantageous to connect a flow meter between blower 8 and aperture 23 whereby to measure the volume of air introduced into tubing 5. Thus, by knowing the distended length of tubing packed into a projectile, and the volume per foot which the tubing holds, it is easily possible to calculate the location of any blockage in the conduit by which my projectile is obstructed and excavate for its removal.

When the projectile has emerged from the conduit into exit manhole 3, the tubing is detached from the projectile, the leading end 17 opened out, and wedged against the exit end of the conduit by means of the element 7 which may take the form of a bell ring. The opposite end 22 of tubing 5 is now twisted into twine form and tied to a hook 23 or ring secured to the chuck of a rotary drill 24 or the like. Upon rotation of the drill, obviously the whole length of tubing will gradually be converted into the twine form depicted at 25 while air is exhausted as indicated by arrows 26 through the aforesaid bell ring 7.

I do not wish to be confined to the particular details of my invention as hereinbefore described. It may for instance be found desirable to employ a yieldable method of anchoring the leading end 17 of my tubing, and in fact to anchor the same a considerable distance back from the leading end so that there will be tubing in manhole 3 which can back up into conduit 1 to compensate for the shortening which may occur during the aforesaid twisting process. Accordingly, in speaking of the leading end of my tubing I do not necessarily refer to the extreme leading end but to the possible several feet of leading end tubing which may be necessary for the purpose aforesaid.

Likewise due to the considerable torsion upon the rear end 23 of tubing 5 in the twisting process aforesaid, it may be found desirable to allow several feet of tubing behind the point at which it is tied to the source of rotation 24 in order that the tying points (or points at which the rear end of the tubing is secured to element 24 by any means) to be progressively backed up. In fact an indeterminate length of tubing may have to be allowed for this purpose according to the distance between manholes in each case. Thus, with regard to the accompanying FIGURE 2 it must not be assumed that the extreme rear end of tubing 5 is necessarily secured in the manner I have described by element 6 since much will depend upon the characteristics of the tubing.

Accordingly, since various modifications can be made in the invention hereinbefore described, and as illustrated in the accompanying drawings, and numerous variations made thereto all within the spirit and scope of the invention without departing from such spirit and scope, it is intended that the said description and drawings are to be interpreted as illustrative only, and not in a limiting sense, and that only such limitations should be placed upon my invention as are specifically contained in the definition thereof as expressed in the accompanying claims.

What I claim as my invention is:

1. As a step in the transmission of cables and the like through conduit lying in situ, the method of conveying a draw-string through said conduit which consists of projecting a length of flexible tubing sealed at the leading end thereof and secured in the vicinity of one end of said conduit, through said conduit by the introduction of uid into said tubing, said tubing being pre-packed, and caused by the pressure of said uid to become unpacked and inflated as it proceeds through said conduit to an open terminus, and then employing said tubing as a drawstring by attaching one end to the member to be pulled through said conduit, and thereby pulling said member through said conduit.

2. In the method of claim 1, the step which consists in converting said tube into twine-like form.

3. In the method of claim 1, the step which consists in converting said tube into twine-like form by twisting from one end thereof after unsealing the opposite end, and while holding said one end anchored and open for the escape interior gaseous lluid therefrom.

4. The method of placing a long flexible member in a duct comprising (1) inserting into one end of said duct a package containing a relatively long length of flexible, ilamentary tubing compressed axially into a relatively short annular accordion pleated form, the end of said package entering said duct first having the tube end thereat sealed and the tube end at the other end of said package being open; (2) securing said tubing at the open end thereof at said one end of the duct; (3) connecting the open end of said tubing in fluid tlow relation with a source of fluid; (4) impelling said fluid into said package at a relatively high rate of flow and at a pressure above that normally present in the duct, whereby the iluid forced into said package causes said tubing to unfold and simultaneously' drives said package forward through said duct to the other end thereof; and (5) using said extended tubing as a draw string for drawing said rlexible member into said duct.

References Cited in the tile of this patent UNIFIED STATES PATENTS 252,956 Loane Jan. 31, 1882 714,903 Hinds Dec. 2, 1902 895,412 Badger Aug. 11, 1908 1,256,520 Coughlin Feb. 19, 1918 2,794,758 Harper et al. une 4, 1957 2,930,584 Hensley et al. Mar. 29, 1960 3,006,607 Hamrick Oct. 31, 1961 3,020,192 Stephens et al. Feb. 6, 1962 

1. AS A STEP IN THE TRANSMISSION OF CABLES AND THE LIKE THROUGH CONDUIT LYING IN SITU, THE METHOD OF CONVEYING A DRAW-STRING THROUGH SAID CONDUIT WHICH CONSISTS OF PROJECTING A LENGTH OF FLEXIBLE TUBING SEALED AT THE LEADING END THEREOF AND SECURED IN THE VICINITY OF ONE END OF SAID CONDUIT, THROUGH SAID CONDUIT BY THE INTRODUCTION OF FLUID INTO SAID TUBING, SAID TUBING BEING PRE-PACKED, AND CAUSED BY THE PRESSURE OF SAID FLUID TO BECOME UNPACKED AND INFLATED AS IT PROCEEDS THROUGH SAID CONDUIT TO AN OPEN TERMINUS, AND THEN EMPLOYING SAID TUBING AS A DRAWSTRING BY ATTACHING ONE END TO THE MEMBER TO BE PULLED THROUGH SAID CONDUIT, AND THEREBY PULLING SAID MEMBER THROUGH SAID CONDUIT. 